Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Batteries, Chargers, and Battery Management Systems.
Post Reply
StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 22 2019 6:26am

Somebody please help punch some holes in my idea here. Home depot has the these 18Volt 9aH batteries for $140 for a 2 pack:

https://www.homedepot.com/p/RYOBI-18-Vo ... /304740785

According to the safety data sheet, it uses Sony US18650VTC6 cells: https://images.homedepot-static.com/cat ... 12c4c2.pdf

According to this here:
https://toolcraze.net/usa-ryobi-9-0-ah- ... ally-here/
"this 9.0 ah battery gets it’s extra large capacity because it houses a total of 15 individual battery cells in three rows of 5 cells stacked."

I'm guessing what they mean is this is a 5S3P battery.

If I buy two of these two packs, I can string them together in series for effectively a 20S3P battery. Doesn't seem like too bad of a deal for $300 after taxes and it comes with a 3 year, warranty. Easy exchange at any Home Depot.

Each cell can do 15 amps continuous, so a 3P should be able to do 45 amps, which would work perfectly with my BBSHD at 72volts using the Phaserunner.

The only question is if the internal BMS will allow the battery to put out 45 amps.

Bonus is I have Ryobi tools anyways, so these will serve multiple purposes. What do you guys think?

User avatar
spinningmagnets   100 GW

100 GW
Posts: 12240
Joined: Dec 21 2007 10:27pm
Location: Ft Riley, NE Kansas

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by spinningmagnets » Mar 22 2019 7:55am

If you break them down, it would be a great source of authentic VTC6 cells. If you tear them apart (which may not be necessary) try to keep the welded nickel tabs between every two cells. Doctor Bass has a lot of old threads where he shows how to wire up a pack with salvaged Makita cells that still have a little bit of spot-welded tab connected to them.

edit, incorrect information deleted so as to avoid confusing researchers...

StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 22 2019 8:47am

SM, always appreciate your insight.

But I'M not following. Why would the individual BMS see 72 volts? I'm planning to keep the whole pack intact and wire them in series. Each BMS should only see 18v, right?

User avatar
spinningmagnets   100 GW

100 GW
Posts: 12240
Joined: Dec 21 2007 10:27pm
Location: Ft Riley, NE Kansas

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by spinningmagnets » Mar 22 2019 10:18am

*brain fart*...yeah, that sounds right.

User avatar
fechter   100 GW

100 GW
Posts: 15407
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by fechter » Mar 22 2019 11:14am

StinkyGoalieGuy wrote:
Mar 22 2019 8:47am

But I'M not following. Why would the individual BMS see 72 volts? I'm planning to keep the whole pack intact and wire them in series. Each BMS should only see 18v, right?
But if one of the three decides to trip, the load (controller) drops to zero and puts the full 72v across the tripped one, which may exceed the rating of the parts and smoke. To avoid this, place a hefty diode across each pack in the non-conducting direction. Normally the diode does nothing. If a single pack trips, the diode carries the current from the other two packs around the tripped one and prevents the voltage from going over.
BMS in series config.jpg
BMS in series config.jpg (19.66 KiB) Viewed 1307 times
"One test is worth a thousand opinions"

StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 22 2019 11:31am

Thanks, Fecter. So I need a diode that can handle at least 72volts, 45amps, assuming my max current draw will only be 45amps?

User avatar
fechter   100 GW

100 GW
Posts: 15407
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by fechter » Mar 22 2019 1:03pm

Right. You can probably get by with a lower current rating as your controller should trip on LVC if any packs go out. If one pack drops out and you keep running the motor, the diode will get very hot. It's hard to miss a sudden 18v drop in battery voltage, so you need to stop right away if you feel this.

Since I'm cheap, I tend to use parts I have on hand instead of buying new ones. You can use a FET like a IRFB4110 as a diode. Just tie the gate to source.

If I had to buy diodes, I'd probably use STPS20SM120SFP
https://www.mouser.com/ProductDetail/ST ... JG0Q%3D%3D
100V, 50A Schottky diode. $1.22 ea.
"One test is worth a thousand opinions"

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 22 2019 1:15pm

18650 VTC6 cells alone are worth $5-7 each.

So really what you're buying - at the cost of some extra labor - is the assumption that they are guaranteed to be "A quality" from the Murata (no longer Sony) factory.

Which is not to be sneezed at given sleazy sales channels that abound in this sub-market.

If you do buy from HD and make use of the packs as built and keep them intact you may even get a little warranty protection.

But maybe not, it is possible there are chips internally counting cycles, recording peak / lowest voltages applied etc.

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 22 2019 1:22pm


LiMn2O4 chemistry, LI manganese oxide 

recent test / review viewtopic.php?t=99016


Other threads https://www.google.com/search?q=vtc6+si ... Fforums%2F


Each pack 5S3P is 18V at 9Ah, so 3Ah / 3.6V nominal per cell, a pack of two is 324Wh or 43¢ per Wh

Using 100Ah @ 12V in LFP at $1000 for comparison, that's 1320Wh or 76¢ per Wh

So Pro's: cheaper, lots greater energy density

not sure about C-rate discharge

Cons: much lower cycle longevity, higher thermal runaway / overtemp risks

StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 22 2019 3:53pm

fechter wrote:
Mar 22 2019 11:14am
StinkyGoalieGuy wrote:
Mar 22 2019 8:47am

But I'M not following. Why would the individual BMS see 72 volts? I'm planning to keep the whole pack intact and wire them in series. Each BMS should only see 18v, right?
But if one of the three decides to trip, the load (controller) drops to zero and puts the full 72v across the tripped one, which may exceed the rating of the parts and smoke. To avoid this, place a hefty diode across each pack in the non-conducting direction. Normally the diode does nothing. If a single pack trips, the diode carries the current from the other two packs around the tripped one and prevents the voltage from going over.

BMS in series config.jpg
I'm still trying to wrap my head around this. It's been a while since I have dealt with anything beyond 1s and 0s. If one of the BMSs trip, why does the load from the controller drop to zero? Is it because the tripped BMS trips open so now it is an open circuit, so current drops to zero, and thus load drops to zero? I assume that's not correct as an open circuit would mean no load on anything.

Or is it the FETS in the BMS are open upon tripping, so the that battery is removed from the circuit, but the current from the other batteries continue to flow through the tripped BMS? So now you see the voltage difference from the positive end of the upstream BMS to the negative end of the downstream BMS? In that case, it should only be 54 volts, right (assuming 4 18V packs in series, one dropping out, leaving 3 18V)? Which is probably still exceeding the voltage specs of the tripped BMS.

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 22 2019 5:11pm

So far when everyone here's talking "BMS", only talking about whatever protection circuitry Ryobi built internally to these 18V/9Ah packs right?

I would think it better to strip the cells out.

Building a custom enclosure to mount them securely, and the matching "jacks" for the pack's proprietary "plugs"

would not be a trivial project.

Nor very space efficient.

What sort of EV is the use case here?

StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 22 2019 5:20pm

john61ct wrote:
Mar 22 2019 5:11pm
So far when everyone here's talking "BMS", only talking about whatever protection circuitry Ryobi built internally to these 18V/9Ah packs right?

I would think it better to strip the cells out.

Building a custom enclosure to mount them securely, and the matching "jacks" for the pack's proprietary "plugs"

would not be a trivial project.

Nor very space efficient.

What sort of EV is the use case here?
Correct. The use case here is for a an electric bike. I'm willing to trade space inefficiency for a robust, pre-built package that comes from a reputable manufacturer that can build batteries that will survive the abuses that power tools typically encounter and have adequate protection against fires. I don't think I could build a package like that myself without spending a lot of effort.

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 22 2019 9:50pm

Well the space inefficiency keeping the packs intact IMO means that

fitting enough oomph and range will not be possible on a bike, either full stop, or at least not without it looking really really strange, maybe going to the rear rack as well as within the triangle?

Here is the charger for comparison
https://www.ryobitools.com/power-tools/ ... percharger

ga2500ev   10 mW

10 mW
Posts: 22
Joined: Mar 23 2012 7:46am

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by ga2500ev » Mar 23 2019 8:13am

Thanks to the OP for pointing out that the batteries are on sale. I'd been looking at them, but they are not in stores and haven't had a sale price in a while. I ordered 5 batteries total, as a single is also on sale for $79. I have an immediate use of a pair as a E-mower battery replacement, a longer term E-bike project for another pair, and just add one to my tool collection for extra power.

I've been looking at both the 18V and 40V Ryobi batteries for project use for a while. The biggest issue with both types is the rather advanced BMS/Power management boards attached to each battery. While designed to protect the battery from major abuse, it's done by being very conservative and quirky. Conservative in terms of overcurrent and overtemp power cutoffs. Quirky as the boards provide limited power to the terminals until current is drawn. You'll see it in the literature as "sleep mode". These behaviors make unmodified batteries quite unreliable outside of their intended scope of operation, and annoying within it. Just yesterday I was trimming some heavy grass with my 40-volt based trimmer and the overcurrent kept cutting out for example. There are a few threads here discussing the issue.

This instructable: https://www.instructables.com/id/Make-a ... ltipurpose points towards the right idea: Add an alternate connector, specifically one that bypasses the BMS. While this particular instructable fails to do the latter, it shows the basic premise. To complete the project requires an understanding of the connection between the board and the cells. Fortunately each board is clearly labeled and it's rather obvious where the solder points connect the cell terminals to the BMS. Each point is labeled CL[num]{+-} where I guess CL means cell, the number is the number position of the cell, which is 1-5 for 18V and 1-10 for 40V batteries, and the +/- are the positive and negative terminals of the cell respectively. Since they are linked in series, the interior connections will only be CL[num]+. But CL1- is battery ground and CL[maxnum]+ is the positive terminal for the raw battery pack. Add a connector to those two and gain access to the battery bypassing the BMS.

What I haven't figured out yet is how the BMS reacts when the battery is bypassed. It's unclear if sensing the BMS power terminal will give overcurrent or overtemp signals even when not pulling power from that terminal.

Even though the pack is a bit clunky with its terminal stalk, I'd probable leave it in place if for no other reason that it can still be charged with a standard charger and can be used in standard tools.

Hope this helps,

ga2500ev

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 23 2019 9:52am

Just realize that any such mods will void your warranty (only if bought at HD!) just as much as if you pulled the cells out completely.

ga2500ev   10 mW

10 mW
Posts: 22
Joined: Mar 23 2012 7:46am

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by ga2500ev » Mar 23 2019 11:48am

john61ct wrote:
Mar 23 2019 9:52am
Just realize that any such mods will void your warranty (only if bought at HD!) just as much as if you pulled the cells out completely.
Virtually all failures of these packs are due to the BMS/power management system. As stated above it's ultra conservative. So any fault detected will shut the battery down though the cells are often perfectly intact. HD would rather replace than to risk any type of castostrophic failure. So at the least little fault they won't discharge or charge through the BMS.

Bypassing it solves the problem. But again leaving everything else intact facilitates normal usage and charging.

Agreed that any tampering voids the warranty. It's the price of utility at a decent price and a good prepackage.

ga2500ev

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 23 2019 3:05pm

For different use cases where maximum energy - to - space density is not important, I agree there are advantages to using the standard pack enclosure.

But then you do need to fabricate custom reverse-engineered holders to both securely clamp the packs in place, and maintaining a reliable electrical connection.

I see that as being **at least** as challenging as using a much more compact enclosure for the bare cells, either bought or DIY.

So, a continuum of use cases:

non-propulsion, low C-rates, leave pack as is

higher C-rates, space/shock/vibration not as much an issue (go-kart, ATV?) bypass BMS otherwise leave physical pack intact

but for a bike I just can't visualize a DIY space efficient mounting system, so IMO these packs are just a great source for top quality VTC6 bare cells at a reasonable price.


StinkyGoalieGuy   100 W

100 W
Posts: 289
Joined: Apr 23 2008 3:53pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by StinkyGoalieGuy » Mar 23 2019 3:19pm

john61ct wrote:
Mar 23 2019 3:05pm
But then you do need to fabricate custom reverse-engineered holders to both securely clamp the packs in place, and maintaining a reliable electrical connection.

I see that as being **at least** as challenging as using a much more compact enclosure for the bare cells, either bought or DIY.
Thingiverse has a bunch of designs already, just need to print them out. I agree, not everyone has access to a 3D printer.

For me, if I can fit all 4 batteries into my frame, then that's more than enough range for my use case. I only need 240watt-hours for my daily commute.

I already have batteries built from harvested cells. But I like the idea of pre-packaged cells in a nice robust package with a built in BMS from a reliable vendor.

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 23 2019 4:41pm

Well the BMS may be what prevents it from working.

But that can be bypassed and still leave the physical pack casing intact.

I'd at least rough it out in SketchUp, maybe you're right, if you only need 4x 9Ah packs, don't need to separate them for charging,

get them somehow lined up in a single cylindrical shape would be pretty low profile, what under 5" wide?

User avatar
Matador   100 kW

100 kW
Posts: 1046
Joined: Jun 29 2016 10:00pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by Matador » Mar 24 2019 8:23am

john61ct wrote:
Mar 22 2019 1:22pm
LiMn2O4 chemistry, LI manganese oxide 

recent test / review viewtopic.php?t=99016


Other threads https://www.google.com/search?q=vtc6+si ... Fforums%2F


Each pack 5S3P is 18V at 9Ah, so 3Ah / 3.6V nominal per cell, a pack of two is 324Wh or 43¢ per Wh

Using 100Ah @ 12V in LFP at $1000 for comparison, that's 1320Wh or 76¢ per Wh

So Pro's: cheaper, lots greater energy density

not sure about C-rate discharge

Cons: much lower cycle longevity, higher thermal runaway / overtemp risks
Unlikeluly LiMnO2. I think they are LiNiMnCoO2. Sony hasn,t used the old spinel since the VTC3. Thr NMC is far superior an tolerant than spinel.

john61ct   100 GW

100 GW
Posts: 7818
Joined: Dec 18 2018 2:06pm

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by john61ct » Mar 24 2019 9:31am


Matador wrote:I think they are LiNiMnCoO2. Sony hasn,t used the old spinel since the VTC3. Thr NMC is far superior an tolerant than spinel.
I see, INR vs IMR, good stuff


docw009   100 kW

100 kW
Posts: 1458
Joined: Aug 02 2015 7:43am
Location: Chicago area suburbs.

Re: Ryobi Sale - hack together a 72V, 9Ah, Sony VTC6 battery for ~$300

Post by docw009 » Mar 24 2019 4:25pm

StinkyGoalieGuy wrote:
Mar 22 2019 6:26am

The only question is if the internal BMS will allow the battery to put out 45 amps.

Bonus is I have Ryobi tools anyways, so these will serve multiple purposes. What do you guys think?
I had the basic Ryobi "40V" 10S-2P pack for my weedwhacker and found that I could ride around for a little bit with my ebike. That had a 22A controller, I believe the Ryobi was 2.6AH.

So I picked up the 5AH version for about $130 from Home Depot. It's also 10S-2P, but they put 2.5AH cells into it. It would reset if I tried to pull 20A thru it, whereas the smaller could handle it. Oh well.

Post Reply