Sterling Battery-Battery Maintainer 12V-12V, 3A

  (1 Review)
Price:  £55.77   (£46.48 Exc. VAT)

Product code:  P02157



In stock

The Sterling Battery-Battery Maintainer is a simple, low cost solution to preventing your battery self-discharging and becoming damaged; keeping it in optimum condition and extending service life.

The Maintainer works by allowing some of the charging current supplied to one battery by a 12V DC charging source (e.g. mains charger, alternator, solar, wind) to be diverted to a second battery to keep it maintained.  A typical use for this device would be where you have a leisure/auxiliary battery being charged by a mains charger or solar charger and you wanted to keep a starter battery maintained using some of this power. It can be used with any combination of battery chemistries (lead-acid & lithium for example), providing they are both at a nominal system voltage of 12V DC, and supplies a 3A max. charge current once the source battery has reached 13.3V. When the source battery reduces to 12.8V the unit will go into standby mode.

The Maintainer is simple to install, being fitted in-line between the positive terminals of the two batteries with 10A fuses (recommend by Sterling). It also requires a negative connection that must be 'common' with both batteries.

Its IP65 rating and ignition-protected design make it particularly suitable for use in harsh marine environments.


  • 3A max. trickle charge between two 12V batteries (or banks of batteries)
  • Works with all battery chemistries and combinations
  • LED indicator lights to show charging & battery status
  • Over-temp, over-voltage and reverse-polarity protection
  • Aux battery low-voltage warning
  • Low self-consumption (uses FETs rather than relays)
  • IP65 rating and ignition-protected for marine use

Further information

This device is not intended to be used to 'bulk' charge a heavily depleted battery as it has no multi-stage charge capability and the current is too limited. It is for maintenance charging to support small loads (approx. 0.5A continuous drain) and prevent self-discharge.

  • Compatible battery types: Lead-acid (wet, gel, AGM) & lithium
  • Nominal system voltage of 'source' battery: 12V DC
  • Nominal system voltage of battery being charged: 12V DC
  • Max. trickle charging current: 3A
  • Activation voltage: 13.3V DC
  • De-activation (standby) voltage: 12.8V DC
  • Current self-consumption: <2mA
  • Protection rating: IP65
  • Reverse polarity protection: Yes (via on-board fuses)
  • Over-temperature protection: Yes (unit shuts down at 80°C)
  • Over-voltage protection threshold: 15.5V DC (unit will shut down)
  • Aux battery low voltage warning threshold: 12.6V DC and below
  • Ignition protected: Yes
  • Supplied cable length: 1m
  • Overall dims: 140 (L) x 45 (W) x 40 (D) mm

Part Number:  BM12123

Average Rating (1 Review):  
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Prompt delivery as always, quality product.
Thursday, 10 June 2021  | 

Brilliant service as always, Sterling battery to battery maintainer being used to feed back/ maintain started battery via solar. Working perfectly.

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