Welcome to Manins' truck camper project

Start Battery

The start battery is specified as 12 V 100 Ah, 760 CCA made by Exide for Iveco.

A possible replacement is Delkor Calcium N70ZZL. Another is Exide Endurance version N70ZZLMF which is 730 CCA 90 Ah ($180 on eBay); it has the ledge on the bottom. Also Exide Extreme XN70ZZLMF which is a larger 810 CCA Battery.

Or SuperCharge MF95D31LW 110 Ah, 810 CCA. $230 on eBay at AutObarn.

Standby Battery Drain

Suspicious about the drop in battery voltage if left for several days, I measured the standby current at the battery by lifting the connector from the negative pole and interposing an ammeter. This is with solar (trickle charge) disconnected, and after sufficient time that various timed consumers closed down (such as dash cam).

  • With BEP Start Battery Switch OFF, current = 0 mA.
  • With BEP Start Battery Switch ON, current settles over time to ~ +1 mA to -5 mA (i.e. ~ 1 mA supplied by House Battery or discharge of 5 mA.
  • With Start Battery Switch ON and House Battery Switch OFF, current ~ -47 mA.

I conclude that if the House Battery were to be absent or switched OFF, the Start Battery has a standby drain of about 47 mA. But with it switched ON, the standby drain settles to no more than about 5 mA. Both are very low and should cause no problems.

The standby current for the Start Battery can be reduced to 0 mA by switching the BEP Start Battery OFF. Any requirements are met by the House Battery.

With only two years ownership (say 3 years total life) the start battery seems to be deteriorating too quickly.

A Possible Explanation

Since the start battery and house battery are joined through the BEP DVSR in normal operation (see Alternator Control) the start battery cannot be charged to any higher voltage than that of the house battery — that is, to no more than 14.1 V, and even so that rarely happens in an actively used camper. The usual maximum voltage is 13.2 V. This is probably not high enough to charge the start battery fully.

One solution is to use a DC-DC charger between the start battery and the house battery. I have however chosen to simply use the switch in the camper to keep the DVSR open-circuit. The alternator can then charge the starter battery to whatever voltage it is set up to do.