Greenworks 40v G-MAX disassembled- 11C rating?

Hi folks, I'm new here. Just put together a light assist setup on a 700c hybrid bike with a Q100, 12a elifebike controller modified to 18a, and a Greenworks 40v 4ah g-max battery. I read/learned a lot on here before jumping in, lots of great info here!

I gambled on the g-max battery after reading the post below.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=46110

EVEE was right, this battery is awesome. Here's the scoop after taking it apart. (tamper resistant torx bit required, then peel the labels, the bottom one will stretch/deform so don't do this if you want to keep it under warranty.)

-UR18650RX cells. From what little I can find, these are 22amp rated (11c), and Greenworks claims up to 2,000 cycles. (44a rating on the 4ah pack sounds about right given a single 2ah battery can power a mower that supposedly is nearly as powerful as a gas mower.)
-20 cells 10s2p (the 2ah battery is 10s1p, they must use the same bms as there is a box checked for either 2p or 1p)
-41.5v on the outside terminals at full charge.
-60 amp fuse on top of the bms.
-4ah pack weight 2.8 lbs. (my full bag weight with 2 batt's/charger/tools is right at 10lbs.)

*Edit* Link 1 shows a 10a(5C) discharge graph, about .3v drop. Link 2 is a PDF of some sort of presentation which is calling this a 20a cell and shows a 20a(10C) discharge graph (see page 21-22) with about .4v drop.
http://www.panasonic.com/industrial/includes/pdf/UR18650RX.pdf
http://media.nmm.de/54/sonnemann_panasonic_15.11.2012_15.00_26769354.pdf


I bought my first battery on amazon for $120 shipped, and charger for $30 shipped. After seeing what cells it had, I bought a complete mower on ebay that came with a 4ah battery and charger for $110 shipped. I think this was a return or display model because it looks brand new. Haven't tried mowing with it yet, but don't really care how it performs since this was a good deal for a spare battery/charger only.

So for the single battery installation, I took apart the charger and soldered wires to the back of the pins and use that in the bag as the battery holder. The + terminal isn't even used on the charger. I just leave it all in the bag to charge. Now that I have a spare battery, the second one fits in the bag and just takes a few seconds to swap out.

*Question- what effect would running these two in parallel have on battery life and range? Since I'm only operating at about 40% of the rated amps with 1, would running 2 provide much of a benefit? I don't want to just cram spade connectors into the battery terminals, seems like an accident waiting to happen. The second charger won't fit into the bag and I don't want to cannibalize that one just for the connector. Thoughts?

Thanks!

I would find a way to parallel them. If they like being used at half the rated 11c rate, they will like it even more to be used at 2c. Figure out some good way to make a plug to use them paralleled. Likely you don't want to disassemble much, so you can still pop one into that mower next summer.

Nice job getting the mower without a battery for a hundred bucks. And you got a good battery too? Nice. Musta fell off a truck, nudge nudge wink wink.

More of these batteries for $120:

http://www.northerntool.com/shop/tools/product_200596743_200596743?cm_mmc=Google-pla-_-Power%20Tools-_-Power%20Tool%20Accessories-_-32911&ci_src=17588969&ci_sku=32911&gclid=CN7c2M3xobsCFYg-MgodYgkAaQ

-Warren.

Reading too fast, I thought these were 24v. 120 for 40v 4 ah is not so bad, not for an 11c cell if that is really true.

Let us know how much sag under load you get, at full speed. Sag from v at that moment, not from full charged. If 4 ah will run a 20 amps controller with only a volt or so of sag, then it's a pretty good c rate for sure.

wow do you have a picture of the inside? are they really Sanyo cells? If so that is awesome.

too bad I have like 8 of the older ones..

Come people, this is not a 40V battery pack. It's a 10s2p 36V liIo pack they rate at 36.5V that comes in at $0.82 per wh. A 5ah real 44.4v pack of rc lipo cost ~$75 and comes in at ~$0.31 per wh, and you don't have to take them apart to use them. Is everyone nuts, or am I missing something. Don't shoot the messenger.

I question 11c rating ?

In my opinion rc lipo is to dam volitile and delicate one screwup and puff up like a blow fish. At least li-ion is a little more forgiving and the green works packs have a BMS onboard if you decide to leave it intact

36v, 40v, whatever. I was just saying I thought at first the price was really high, confusing them with the 5 or 6s variety. Not so bad, for a 4 ah 10s pack with a high quality cell in it.

We all know you can get cheap lico, cheap. Doesn't make it best for everybody. This is for a mild assist build, and 4 ah might well take him many miles used that way. So the cost per wh won't matter as much as it does for folks that need 50wh/mi, like I do.

But 2000 till the bms trips cycles at 11c? Yeah right. But 8 ah of it would allow a 16 amp flow at 2c. If it does that with very little sag, muy bueno. It sounds better to me than a tiny frog battery.

I'm gonna try and get a reading of amp draw from this mower when and if one comes into my job I will be using a fluke amp clamp for measurements

Here's the only picture I took when it was apart. The cells do seem to be legit.

Regarding the C rating, Greenworks advertises "up to 60 minutes run time" on the bigger mower that comes with 1 4ah and 1 2ah battery. That means up to 20 min on the small battery. My guess is this is optimistic for thin grass on a higher setting. If you only got 15 min, that's an average of 4C, I'm sure with spikes much higher than that. If they engineered these properly, I would think it needs a minimum 8C battery.

I checked voltage drop, but it's about 10 degrees outside and the batteries were 30-40 degrees in the garage. It's about a 2-3v drop at full load. I'll see what it looks like at normal temperatures. Seems like running them in parallel would be a good idea though. Thanks for the feedback guys.

wesnewell said:

Come people, this is not a 40V battery pack. It's a 10s2p 36V liIo pack they rate at 36.5V that comes in at $0.82 per wh. A 5ah real 44.4v pack of rc lipo cost ~$75 and comes in at ~$0.31 per wh, and you don't have to take them apart to use them. Is everyone nuts, or am I missing something. Don't shoot the messenger.

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I considered this, but lipo is just not for me right now. My kid's room is above the garage where all this stuff sits, and it's just not worth it to me to save a few bucks when safety is a concern. I wanted a battery that I could plug in and forget about. And yes, it's only a 36-37v battery, marketing hype I guess.

These things really don't look so bad to me. 10S2P of the newer Sanyo cells reminds me of my old Fatpacks that we still use regularly. They were 10S2P Sony V or VT cells but Bosch listed them @ 36 volts. They do charge to 41 or so volts. The bad part is the price. Fatpacks were 45 bucks apiece delivered. That was 3-4 years ago though. Times change but fatpacks were only 2 amps. These packs are 4 amps. Similar price per watt, I guess. Not terrible.
otherDoc

Has anyone tried to see what the maximum current is on the BMS before it cuts out ?

Gab said:

Has anyone tried to see what the maximum current is on the BMS before it cuts out ?

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evee reported pulling 30 amps on his g-max 4ah without hitting any current limiting (this was in the thread linked in the first post above.)

dogman said:

I would find a way to parallel them. If they like being used at half the rated 11c rate, they will like it even more to be used at 2c. Figure out some good way to make a plug to use them paralleled. Likely you don't want to disassemble much, so you can still pop one into that mower next summer.

Nice job getting the mower without a battery for a hundred bucks. And you got a good battery too? Nice. Musta fell off a truck, nudge nudge wink wink.

Click to expand...

I'm thinking more about paralleling these. Looks like the whole connector/wiring from the mower comes out easily and is pretty compact to fit in the bag. If I ever wanted to use the mower it would be quick to reinstall. Question on charging- What would happen if the second battery was installed in a lower state of charge than the primary? To avoid problems with this, they probably always need to be charged together, or fully charged when connected right? What about using the one charger with both batteries connected? The second battery would only be connected at the +/- terminals, so I assume it would charge to the same pack voltage but not balance the cells? Would it be safe to do this and then every once and awhile take it out and use the spare charger to balance? (newbie on this stuff.) Thanks.

docnjoj said:

These things really don't look so bad to me. 10S2P of the newer Sanyo cells reminds me of my old Fatpacks that we still use regularly. They were 10S2P Sony V or VT cells but Bosch listed them @ 36 volts. They do charge to 41 or so volts. The bad part is the price. Fatpacks were 45 bucks apiece delivered. That was 3-4 years ago though. Times change but fatpacks were only 2 amps. These packs are 4 amps. Similar price per watt, I guess. Not terrible.
otherDoc

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I'd say so too considering the safety factor and also if you were to incorporate the tools into your yard arsenal. I have a ryobi 40v trimmer that is way better than my gas trimmers for medium use. Would be very practical if you want all cordless mower, saw, weedeater and ebike!

There is one on eBay right now for 70usd in california: http://www.ebay.com/itm/NEW-GreenWo...US_Rechargeable_Batteries&hash=item5d46e49669

agniusm said:

There is one on eBay right now for 70usd in california: http://www.ebay.com/itm/NEW-GreenWo...US_Rechargeable_Batteries&hash=item5d46e49669

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careful that is the first run packs(non G series) there is a separate thread on them, They are not 11c Sanyo cells.

Added two links to the original post with some technical spec's on these cells. Looks like they are at least 10C cells. I feel a bit better about just running 1 pack at a time at 4.5C max. The controller LVC of 31.5v (3.15v/cell) looks about right for this.

I'm still considering running two in parallel, but only if there would be a meaningful improvement in battery life (eg. 2,000 cycles instead of 1,000.) Thoughts?

My hang up is on the charging. With one battery connected to the charger in the bag, what would happen if the second battery was just paralleled at the +/- outputs? Does the "charge" terminal need to be used for balanced charging? And if these were paralleled that way, could the +/- stay connected during charging?

If you want to charge both with 1 set of output terminals you will have to parallel the red/black main leads as well as every single balance wire to the first board where you plan to charge.

I would probably also take off the 2nd charging board that would be useless at that point. there may be a way to charge both boards together, but it may cut the charge time in half creating the same exact effect in reverse. unless you get a higher output charger.

Cant u just charge them seprately with 2 chargers and then wire them up with 2 harnesses and discharge them in parallel?

If it works anything like my Fatpacks you can use 1 board in the charger and charge as many packs as you need to in parallel. I do 6 at once. I did remove the boards from all the packs and just use one in the charger to a parallel connection.
otherDoc

jk1 said:

Cant u just charge them seprately with 2 chargers and then wire them up with 2 harnesses and discharge them in parallel?

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yes!
sounds like the best solution to keep the battery life up and thus the c rate down....

wineboyrider said:

jk1 said:

Cant u just charge them seprately with 2 chargers and then wire them up with 2 harnesses and discharge them in parallel?

Click to expand...

yes!
sounds like the best solution to keep the battery life up and thus the c rate down....

Click to expand...

Yes, this would be easiest. It's just that they could only be paralleled after being fully charged.

skeetab5780 said:

If you want to charge both with 1 set of output terminals you will have to parallel the red/black main leads as well as every single balance wire to the first board where you plan to charge.

I would probably also take off the 2nd charging board that would be useless at that point. there may be a way to charge both boards together, but it may cut the charge time in half creating the same exact effect in reverse. unless you get a higher output charger.

Click to expand...

docnjoj said:

If it works anything like my Fatpacks you can use 1 board in the charger and charge as many packs as you need to in parallel. I do 6 at once. I did remove the boards from all the packs and just use one in the charger to a parallel connection.
otherDoc

Click to expand...

I wanted to keep these packs fully functional for single charging or use in other tools.

bluovalguy said:

With one battery connected to the charger in the bag, what would happen if the second battery was just paralleled at the +/- outputs? Does the "charge" terminal need to be used for balanced charging? And if these were paralleled that way, could the +/- stay connected during charging?

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Would this work? Just parallel at +/- terminals and charge the plugged in battery as normal? Or parallel the charge terminals and disconnect + or - while charging? Thanks for the feedback guys.

Charge each by themself's and parelle for discharge. Simple. Do you have two chargers for fast charging ?