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I bought a used electric utility vehicle that normally uses eight lead acid 6 V 260 Ah batteries wired in series. The utility vehicle instead came with four 12 V 105 Ah batteries wired in series. The charger included is a 48 V charger for 140-270 Ah. If I charge the 48 V 105 Ah series of batteries with this 140-270 Ah charger, will they explode or have other ill effects on the batteries, the charger, or the surrounding environment?

The batteries I have are MK Battery 8A31DT https://www.ecodirect.com/MK-Battery-8A31DT-DEKA-12-Volt-104-AH-Battery-p/mk-battery-8a31dt-sealed-agm.htm

The batteries normally used I think are Trojan T145 https://www.trojanbattery.com/product/t-145/

The charger is a Lester Electric Lestronic II Automatic battery charger (can't find an accurate link)

Thanks for any help!

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  • \$\begingroup\$ Should be fine, but the very narrow capacity range stated is worrisome. A good design should take one or two orders of magnitude capacity range. The issue is as always with series charging is that the batteries will become unbalanced over time. \$\endgroup\$
    – winny
    Commented Jul 21, 2022 at 21:38
  • \$\begingroup\$ @winny The manual warns against it. What makes you disagree with the manual? Also, voting for close, because this is not design question, but device usage question, with answer readable from manual. \$\endgroup\$
    – Justme
    Commented Jul 21, 2022 at 21:39
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    \$\begingroup\$ @Justme Several years of designing battery chargers for a living. \$\endgroup\$
    – winny
    Commented Jul 21, 2022 at 21:41
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    \$\begingroup\$ @Justme The “should be” would be a clue here. \$\endgroup\$
    – winny
    Commented Jul 21, 2022 at 21:43
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    \$\begingroup\$ @Finbarr Indeed. Professional equipment like trucks use 2 V cells so just that one with low capacity or high ESR can be replaced. If you do analysis of bad 24 V batteries aimed for recycling, you’ll find a striking number of them having 11/12 good cells inside them but no way to replace the bad one. \$\endgroup\$
    – winny
    Commented Jul 21, 2022 at 22:09

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Quote from manual which should be self-explamatory:

CAUTION: USE CHARGER ONLY FOR CHARGING 48-VOLT, 24-CELL, SERIES CONNECTED WET LEAD-ACID SYSTEM WITH A CAPACITY OF 140 TO 270 AMPERE-HOURS (20 HR. RATE). OTHER TYPES OF BATTERIES MAY BURST CAUSING PERSONAL INJURY AND DAMAGE.

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  • \$\begingroup\$ I suppose it's self explanatory, but why would a battery burst exactly? Apologies, I didn't realize this was a design forum, it was the place that looked like questions of this nature were being answered. Follow up: assuming my batteries risk bursting by being charged by this charger, can I purchase a 48V charger intended for 105 Ah batteries, and charge these in series by connecting the negative to the negative end of the series and positive to the positive end? The advantage the Lestronic charger has is it has the special plug to go directly into the UTV. \$\endgroup\$
    – Goudron
    Commented Jul 21, 2022 at 23:34
  • \$\begingroup\$ If you feel comfortable hacking electrical equipment, you may be able to find out what the Lestronic charger uses for current measurement, and replace it or adjust it to suit the 105 A-h battery pack. It's probably a shunt, which can fairly easily be raised in resistance by removing fins or machining them (drilling holes or filing). \$\endgroup\$
    – PStechPaul
    Commented Jul 22, 2022 at 5:19
  • \$\begingroup\$ @Goudron I suspect the warning is really there to stop people using it for Lithium batteries, which almost certainly WILL be permanently damaged by a lead-acid charger as they cannot tolerate overcharging and may catch fire or explode. \$\endgroup\$
    – Finbarr
    Commented Jul 22, 2022 at 7:58

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