Battery Vehicle Society

ex925 wrote:Er, Chris, (and always remembering how vastly much I don't know about all this.....)
I asked the excellent Mr. Ping about using this 36v pack in series for 72v.dc
He said best in parallel, (because of main cable gauge, I think?)
Does a similar, (lesser?), constraint apply, 24v+36v?
(Just my tuppence worth.....)
All the best
Ed

Not really an issue as I would be within the spec of the output leads.

Thanks for the heads up though.

Also my thinking is if am able to purchase your pack it gives me spares for mine as well

ChrisB

Connecting Ping packs in series can blow the BMS if one pack of the two shuts down because of a low cell condition or because of over-current.

Connecting them in parallel is OK, but best done with a couple of low voltage drop diodes, either Schottky diodes of a suitable voltage and current rating, or better still, a couple of Nick Long's excellent ideal diodes, that have virtually no forward voltage drop at all (I use them on my solar panels to eke out that last little bit of power). Again, this is to help protect the BMS, as one pack may shut down before the other and the BMS may not take kindly to what would look like an attempt to charge the shut-down pack via the discharge connections. The ideal diode info is here: http://www.re-voltage.eu/electronicsID80V2.html

Jeremy

Interesting, I would have thought in series is better than parallel, as if either pack trips the outputs shut down, series circuit and all that ?, where as in parallel if one trips then it means the other pack would then have to put up with the whole discharge current all of a sudden, and I'd suspect that would then trip as well if you were running it that close

ChrisB

I think the series connection problem is down to the way the BMS switches work. There have been several cases where people have blown up these Signal Lab BMS boards by putting them in series without isolating diodes. Ping now sells diodes specially for the purpose, as a consequence of this problem.

Jeremy

I briefly used a schottky diode to safely run the Ping-pack in series with a 36v.dc SLA pack
(This pack comprised 3 22ah.12v.dc golf-trolley batteries, used on the "Junkyard Dog")
The extra boost allowed an extra 8-10 miles range when running in road-legal mode
(Old 36v.dc 4-brush pm motor, [30amp?] controller, a little pedalling [I'm LAZY], and..........)
(Kerb weight with both packs on-board nearly 39kg, 1kg less than the legal maximum!)
On the Yamaha "Easy" EAPC, the 2nd-pack gain was more like 12-15 miles, but even then, it was HEAVY with both packs
Paul did the calculations to determine exactly what kind of Schottky Diode, I emailed Mr. Ping, he approved

No evident detrimental effect on either pack as far as I can judge by comparisons between before and after static tests
N.B. my kind of static tests, 3 12v. halogen headlamps in series, then time taken to lose light-meter values
Pretty damn crude, I reckon, but my best guess to achieve a vague idea of comparative change..............
HTH

All the best
Ed

ChrisB wrote:Put me down for a definate Ed, cheque/cash/bank transfer available on your approval.

Quite happy with the price and the fact its 20ah means it will also match my 24v 20ah pack quite nicely if I ever joined them up

But as Deker gave the heads up first and as a gentleman myself, I bow to him being first in the queue

ChrisB

All yours Chris.

I was opting for the Pb route anyway, Im so impressed with Sonnenschein's long life when used with the proper charger I'll use those.

Deker

Deker wrote:

ChrisB wrote:Put me down for a definate Ed, cheque/cash/bank transfer available on your approval.

Quite happy with the price and the fact its 20ah means it will also match my 24v 20ah pack quite nicely if I ever joined them up

But as Deker gave the heads up first and as a gentleman myself, I bow to him being first in the queue

ChrisB

All yours Chris.

I was opting for the Pb route anyway, Im so impressed with Sonnenschein's long life when used with the proper charger I'll use those.

Deker

No problem Deker, I just didnt want to jump the queue, must admit I think you'd be extra surprised at these LifePO's


Right Ed game on, I'll drop you a PM with how we want to go about sorting the purchase out

ChrisB

If you want to know how to connect Ping batteries in series, you can get a wiring diagram from www.PingBattery.com
Briefly, you put a diode in parallel with each battery pack. These are connected to battery + and the output side of the BMS (not the battery side). Then if one of the BMS shuts down, it will be protected because the current from the remaining battery will shunt around the one that has shut down.
The diodes do have to be of sufficient current rating to take the full output current of the battery, and have a voltage rating equal to the battery voltage.

Jonathan

Is it not possible to get ping to put two (or even more) batteries together under one BMS? For instance, could he not put two of his 20ah ones together in parallel to make a 40ah one under a high rate BMS so they could both be charged by the same charger?

I asked Mr. Ping last summer if he could build a 72v.dc pack for a motorcycle I am building (very slowly!)
He replied that he did not have proven kits for sale at that level presently, however.......
In re 36v.dc packs, he offered an affordable BMS allowing me far more amps
He did warn me that increasing the amps might shorten the battery-life
If you are ready to buy something, why not email Mr. Ping?
He is wonderfully helpful, and patient
All the best
Ed