Depending on the charge rate (amps) used, you can use a battery charger to recharge a discharged battery fast and conveniently.
During the charging process, the battery cables may become extremely hot to the touch.
You may be wondering if this is normal or whether you’d be concerned or not.
This post sheds light on why battery cables can get extremely hot during the charging process and suggests some fixes to get the temperature normal again.
Is this Normal? Should you be Concerned?
The temperature of the battery charger cables during charging should be mildly warm at most but never hot.
Good cable sizing should also factor in the significantly higher current that the cables are subjected to during the bulk charging phase.
You should be concerned if you find them hot. If they’re hot then it is a sign that they are carrying a higher current than they are designed for possibly because of a fault or a cable sizing issue.
Either way, this should be addressed immediately.
Why it is Dangerous for Battery cables to get Hot
The high temperatures can damage the cable insulation, causing it to melt and can start a fire.
What to Do
As a first step, switch off the battery charger to investigate the likely cause of the heating temperatures to avert the associated risks.
What Causes Battery Charger Cables to Become Hot (+ Fixes)
If the battery charger cables are hot to the touch when charging the battery, check:
For a New Installation
#1. If it is a new installation and the battery cable temperature was normal previously, confirm that the battery cables and clamps are appropriately sized for the battery charger current of the charger.
Undersized cables heat up when carrying currents beyond their holding capacity.
| No. | Estimated Current Carrying Capacity (amps) | Battery Charger Cable Size (AWG) |
| 1 | 30A | 10 AWG |
| 2 | 40A | 8AWG |
| 3 | 55A | 6AWG |
| 4 | 70A | 4AWG |
#2. Also, confirm that the battery clamps are firmly crimped to the battery cables.
If the installation has been in service for a while, check:
#1. The battery posts for corrosion. This is common in batteries that have been in service for some time. Remove the bluish-greenish powdery coating on the battery terminals.
#2. Are the cable terminals firmly crimped on the battery posts? Loosely fitting battery terminals increase the resistance to the current flow from the charger which contributes to the high temperature of the battery terminals and cables too.
#3. The battery under charge is damaged. It is also possible that the battery under charge has an internal short and is drawing an unusually high current flow which causes heat buildup in the cables.
Is the battery hot? What is the voltage of the battery?
A deeply discharged or extremely hot battery might be damaged. Have it tested at an auto repair shop or you can use a good quality portable battery tester to check the health of the battery.
Closing Thoughts
The charger’s battery cables should only be mildly warm at most during the charging process. Should they be hot, then there is a fault – could be a cable design or sizing issue, a fault in the cabling, or in the battery.
Potential problem areas to look at are corroded battery terminals, loosely connected or crimped battery cables, and a damaged battery.
Hope this helps!
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