Battery Cable Voltage Drop - Victron energy MPPT 250/100-TR VE.CAN Manual

If the state of charge of the battery is unknown, and the current is reducing while the sun is still shining, it can mistakenly be
interpreted as the solar charger being faulty.
The first current reduction takes place at the end of the absorption stage, when the battery is approximately 80% charged.
The current will continue to reduce during the float stage, when the battery is approximately 80 and 100% charged.
The float stage starts when the batteries are 100% full. During the float stage the charge current is very low.
To find out what the state of charge (SoC) of the battery is, check the battery monitor (if present), or alternatively check the charge
stage the solar charger is in.
• Bulk: 0-80% SoC
• Absorption 80-100% SoC
• Float or storage: 100% SoC

9.3.4. Battery cable voltage drop

If there is a voltage drop over the battery cables, the solar charger will output the correct voltage, but the batteries will receive a
lower voltage. Battery charging will take longer, and this can potentially lead to undercharged batteries.
A VE.Smart network can help in case of a cable voltage drop. A
terminal voltage and sends this via the VE.Smart network to the solar charger. If the battery voltage is less than the solar charge
voltage, the solar charger will increase its charge voltage to compensate for the voltage losses. But be aware that in case there is
a large voltage drop, the battery cables and cable connection will need to be checked and if there are issue they will needs to be
rectified first.
A voltage difference has the effect that the battery will be charged with voltages that are too low to. It will take longer to charge the
batteries because the charge voltage is too low and there is a loss of charge power. The lost power is caused by heat dissipated
over the battery cables.
The voltage drop is caused by the following:
• Battery cables with insufficient cross-sectional area
• Badly crimped cable lugs or terminals
• Loose terminal connections
• Bad or loose fuse(s)
For more information on cabling issues and voltage drop see the
Battery cable voltage drop check
This check can only be performed if the solar charger is in the bulk charge stage and is charging with full current.
1. Measure the voltage on the battery terminals of the solar charger using the VictronConnect app or a multi meter.
2. Measure the battery voltage on the terminals of the battery using a multi meter.
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MPPT solar charger manual
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