DPI 48 volt charger shutting off too soon?

[tomtt2]

I have a Yamaha Drive with a 48 volt battery pack consisting of four 12 volt batteries. The batteries are only about four months old and have had about 100 charge cycles. Electrolite is checked regularly and distilled water added if needed. The pack is rarely allowed to drop below 50% charge.

Recently, I noticed a slight drop in range of the cart so checked the specific gravity of each cell after completing a charge cycle. I used a temperature compensating hydrometer with the glass float.

I found that a few cells scattered across the pack had a specific gravity of 1200 while most had SG of 1250. One battery had a cell with SG of 1100 or less while the rest of the cells in that battery were 1250.

I individually charged each of the 12 volt batteries then retested the SG. Every battery but the one with the 1100 reading came up to 1250.

I had the battery with the low cell replaced the recharged the pack. Individual battery voltage was 12.9 on each battery. Specific gravity was around 1250 for all 24 cells.

But here's the question: While talking to the battery distributor about my bad cell, he said that he talked to his tech guys and they thought that maybe my battery charger was cutting off too soon and not fully charging the batteries.

During charge, the voltage across the pack is 57.1 VDC using a digital volt meter. When the charger completes its cycle the voltage drops to 53.4. Twenty minutes after disconnecting the charger, the pack voltage is 51.9.

So, do any of these readings indicate that the charger may be shutting down before the batteries are fully charged?
What is the normal pack voltage during the charge cycle?
What is the normal pack voltage after charging and disconnecting the charger?
Has anyone ever ran across a DPI 48 volt charger that charged, but shut off before fully charging the batteries?

I want to take good care of this battery pack (it costs enough), but I don't want to blindly chase after a new charger without knowing that the old one really has a problem.

Great thanks to anyone who takes the time to read through all of this and offer their experience.

[cgtech]

You should be seeing around 58v at the end of charge cycle if using the trojan profile on the charger.

The voltage desired for the batteries varies by manufacturer. What mode is the charger set to now? What brand batteries do you have?

[DIRTPIT HC]

I also have a DPI charger. My cart has 6/8v batteries 48v that are about 2 mos old. While charging, my cart is in the 57v range and when it goes to float charge it fluctuates between 52.9v and 53v. I don't know about 20 minutes after disconnecting but it does drop and several hours after disconnecting it drops to 50.9v and holds there for at least 24 hours unless driven. I'm sure others will comment but seems to me like your charger is doing it's thing. I am very satisfied with my DPI and I believe you will find many others here that are as well. One thing, if your charger has the mode selector, make sure you have it set to the correct mode for your battery type/brand, but I believe you just had a rep. making an excuse for a bad battery.

[tomtt2]

Thanks for the quick responses. Regarding the mode settings. According to the label on the charger, it is preset to MD3 which is described as "48V, 225 AH Lead Acid Trj". I figure this is a Trojan profile. There are other modes listed for US Batteries, a 150 AH Trojan profile and one 36V profile. I pulled the case cover on the charger to take a look for any jumpers that would allow for a profile change, but didn't see anything that looked like jumpers. I don't have the manual for this charger and couldn't find a PDF version on the DPI site, so I'm a bit in the dark on the charger.

I'm a little surprised that post charge, the individual battery voltages are only in the 12.8 to 12.9 range. I would have expected over 13 VDC fresh off the charger.

The batteries are Crown CR 155s

Any more insights would be appreciated.

[cgtech]

Your charger will either have a door on the front with 2 screws to access the jumpers, or you will have jumpers on the board labled "J3" & "J4". The Trojan mode is the coldest 48v mode on that charger (lowest finish charge voltage). Your SG readings do indicate that your batteries would like a higher finish voltage. And i dont believe the "trojan" mode is the optimal mode for crowns. You could try the "US" mode, then re-check the SG. Have you contacted DPI, they will likely give you the best profile suggestions.

[tomtt2]

Thanks for the specifics. I don't have a door or screws on the front of the charger, so I'll pull the case cover again and look for the J3~j4 labels on the board.

I did email DPI last evening, but haven't heard back.

I'll let you know what I find.
Thanks again.

[cgtech]

Heres an example, this board is set to "Mode 2". The pick is pointed at the jumpers (right next to the second red led).

[tomtt2]

I pulled the cover on my charger and found the jumper as you noted. I confirmed that my charger is set to mode Mode 3 (jumper on J4 only). I pulled the jumper to set the charger to Mode 1 (no jumpers) at the suggestion of one other post. This is apparently the US battery charge profile with an initial charge voltage of 51.7 VDC. I think this is below the Mode 3 charge voltage. I won't need mode 4 since it is 36 volts, so I will not need two jumpers, but I'm still not sure what charge profile is correct for the Crown batteries. Based on testing, I think I'm still under charging them, but don't know which mode would up the charge.




Any suggestions for which mode 1, 2, 3) would be best for Crown batteries?

[cgtech]

The US mode is the "hottest" mode, with the highest finish voltage. What happens when you first plug the charger in doesnt matter nearly as much as the voltage achieved just before the charger shuts off.

[tomtt2]

Thanks! That makes me feel better about changing the mode. I'm pretty sure the batteries need a higher finish voltage to reach full charge. Hopefully, the mode 1 setting will get the job done. Should know in about eight hours.

Regards,