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The New Battery system by Reeds Prospecting
The RPS Li-Ion Battery

Reeds Prospecting Li-Ion Batteries - the Pros & Cons

I have finally tested one of these new systems and have some non biased info relating to them. Overall they are a good system and from a technical point of view they definitely do as advertised by Reeds Prospecting Supplies (RPS). On all they seem quite well manufactured (on the outside). RPS was trying to produce a niche market for lightweight durable batteries, which they did reasonably well considering that they relied upon the R&D of a battery manufacture. This company (which will remain nameless) is a Perth company that supplies Hospital Battery backup systems and is a specialist in battery designs since 1982. Now you would think that having been around for some considerable time that the systems they produce would be extremely good? Well being involved in R&D for over 20 years my self I was surprised when I opened and inspected the units. The following are some photo's of the units that I opened to modify to suit my GPM system.

Inside the RPS Li-Ion

Inside the Battery

This photo shows the inside of the battery. Fairly simple isn't it? Neat and tidy with plenty of space.

Without the battery pack

Without the battery

This photo shows the electronics of it. The regulator is bolted to the case (on left side of photo). To the top is the voltage adjustment pot (seen better in the previous photo with battery). This is a 10/15 turn pot which is really an overkill as the output voltage does not have to be that exact and either way a normal 1 turn pot can still adjust to an accurate voltage level. Unfortunately due to the design (deliberate?) the battery can only be adjusted to a maximum of 7.55V so I had to chuck this out and replace with my regulator to allow the swing. I was building the voltage regulator into this unit rather than supplying another box as in the GPM mod. This way you can still use the battery pack as the 6.9V system and if you decide to buy another detector (like a 3000) you can safely use the RPS battery on that by turning the external voltage adjustment I installed down to 6.9V.

Battery Disected

The Batteries

This photo shows the stripped battery pack. The circuit board you see is all that stops the battery blowing you or your 4WD to pieces when charging and whilst in use. This is referred to as a "Supervisory Circuit", "Safety Circuit" and the list goes on. ALL Li-Ion cells must have this. These batteries are extremely explosive if they get too hot. The circuit monitors this along with current/voltage input and output rates to insure that the cells do not reach critical levels.

If you don't believe how explosive lithium batteries are get a 3V lithium watch battery, use a rubber band or non conductive plastic clamp and place 2 wires (LONG WIRES) + to +, - to -, and apply 3+ volts to it from a decent power source and watch the explosion! I would suggest after saying this NOT to do this. You could hurt yourself! So back to the info..

So this circuit protects the battery pack from this happening. (Hopefully). The batteries are LG 3.6V 2200mAhr. 9 of them in total in a 3 x 3 pack (3 in parallel to give 6.6Ahr and 3 in Series to give 10.8V) Li-Ion packs like this generally charge to 12.6V and drop to as low as 8.3V. I found when running my "modified system" that the batteries lasted 6.5 hrs. From 12.6 to 10V took around 6 hours, the last 1.7V (to drop to 8.3V) took only 30 minutes or less.

The design could have been better. The weight could have been halved if they used a strong plastic box as the regulator could handle being mounted on a small heatsink inside the case. The battery pack weighed in at around 300+gms on the other hand the metal case weighed 400gms! Also I found the on/off switch although very nice fell to bits on one without even touching it!

Disadvantages with the unit will only come to light with time. According to the data (see the battery info pages on this site), Li-Ion doesn't have a long life expectancy. This is true of Notebooks that use exactly similar batteries. Even the LG site specs on these batteries include that with a 40% charge rate the batteries will lose 10-20% of their total capacity after 1 year! This means that if you charged them fully for 144 days a year after the first year you will have a battery that will last (based on RPS quote of lasting 8hrs) between 6-7 hours. At $330 a pot and if you sent them away to get repacked possibly as low as $90 they become a very expensive proposition.

I can see as time goes on and prices fall (new & better Li-Ion batteries are already available) that they could become the way of the future and if you have a bad back or get tired carrying conventional 2Kg SLA batteries then these are definately the only way to go.

See more info at Reeds Prospecting Supplies

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