Charging two 36V batteries using the Cycle-Satiator

Batteries, Chargers, and Battery Management Systems.
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thunderstorm80   1 kW

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Joined: Mar 29 2016 5:54am

Charging two 36V batteries using the Cycle-Satiator

Post by thunderstorm80 » Nov 25 2018 10:26am

Hi,
I bought two Hailong 36V23Ah packs from Grin, and these are configured in series (with pass-diode) at 72V.
Using two 72V5A Satiator chargers would let me max out the chargers at a steady 720W (360*2) from 50% SOC and above. (3.6V@cell@50% - 20*3.6=72V * 5 = 360W for each unit)
The problem is that while doing that is faster and allows live CA monitoring&logging of the current that comes and goes, there is no BMS protection. (it is charged via the discharge port)

To make things reliable, the right approach is to supply each battery with it's own 48V8A model plugged into the charging port. But here, the speed of the charge is much slower since it is current limited through the entire CC long stage.
To give you the numbers, we talk about just 260W on average at the first half of the charge from empty battery, since the voltage would be only around ~30V or so. At 50% SOC it's 37V*8A=296W and just before switching to CV we get 336W, which is also lower than what the unit is capable of. (max 360W)
For the two batteries the charge power will vary from just 520W at the beginning of the charge to 672W at the CC stage end, far from the two unit's spec of 720W.

Since I often charge in gas stations along the way and want to minimize the waiting time, I have two options:
1. Charging using two 72V5A chargers, but to not more than 80-90% SOC on a regular basis. Charge via the charging port when 100% range is needed and for balancing the cells. For this I would like to ask - How often do you think such 100% balance-charge is necessary?

2. Selling the two 36V23Ah batteries and getting two 52V16Ah ones, to work in parallel. The 48V8A Satiator will be 360W "saturated" with this battery from 10% SOC. As you saw from my calculations, there will be a significant difference in the overall charging times!

I chose to work with 72V because you can speed up if you need to temporary merge with traffic, and it means the overall battery current via the wires is much smaller. (and the heat which is lost to the square of that current)
72V also let me charge my laptop/camera using their standard AC brick, if I am happening to be camping away from the grid. (or to charge them while I am rolling)

And last, thinking about the calculations above shows also how a battery cell would be more and more stressed towards the end of it's discharge curve or the end of it's charging curve, while the cell would have preferred this to be in the reverse pattern....

bionx 1954   100 W

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Location: ottawa canada

Re: Charging two 36V batteries using the Cycle-Satiator

Post by bionx 1954 » Nov 26 2018 2:39pm

Hi I have the 72v 5A satiator with 2 36v Bosch battery packs each 12 A. I normally charge them in at 36v@ 5A ( 180watts/hr.)if I am not in a rush. When on the road and need a fast charge I series the 36 v packs and charge at 72V @ 5A (360 watts/hr.)

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