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Reeds Prospecting Supplies Li-Ion Battery

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20 years 5 months ago #31 by Ismael
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 are a good buy. From a technical point of view they definately do as advertised by Reeds Prospecting Supplies (RPS), however,(don't you hate these Howevers?), I have some disturbing facts that will cause you grief eventually.

A brief explanation of Li-Ion batteries is appropriate here so as to further the reason. Li-Ion batteries are generally considered to be the best of the best, light, sturdy and have quite a good recharging life expectancy, that is if they are correctly charged & discharged. Li-Ion packs have a BSU (Battery Safety Unit or supervisory circuit), this controls the rate of discharge (output current/Voltage) and the rate of charge (input current/voltage) to each cell and also monitors temperature. You see Li-Ion batteries are a virtual bomb if not charged and discharged properly. Anyway getting back to the topic, the 3.6 cell charges to 4.1 or 4.2V depending on the type, so in a pack (like RPS's) you have 9 cells 3 in series to give the output voltage and 3 in parallel to give capacity current (3rows x 3columns if you like). Now here comes the setback, when discharged the batteries should be shutdown by the BSU when the cells drop to 3.2V because if you ever try to read the output from a Li-Ion pack when flat you get 0V, but they have been shutdown to preserve their life expectancy. The ones produced for Reeds are LG type cells (see this link: <a href=' www.lgchem.com/html/product/electronic/battery/11.html ' target='_blank'>LG Chemical</a> These are the consumer batteries with the same specs as the LG-OEM cells in the packs. As you can see these have a cutoff voltage of 3V which is still okay even if a little low, unfortunately the cutoff voltage in the RPS unit is 8.4V or 2.8V per cell. Well, .2V per cell doesn't seem much but when you consider that the tests that I performed using an output of 8.5V regulated from the pack it took 6 hours from an initial output of 12.6V to drop to 10V (2.6V drop)and 20 mins to drop from 10 - 8.4V (1.6V drop)the last voltage drop was very dramatic. The BSU should have according to the specs of the cells stopped at 9V. According to LG that after 400 charges the battery pack will perform at 80% from when new that means that after normal discharging the batteries will go from lasting 7 hours - 5.6 hours. Now if we also add in the actual discharge rate which equates to around 15% you get around a 4.5 - 5 hour life after just over 400 days of use. There is of course a way around this and that is NOT TO LET THE BATTERIES GO FLAT! My suggestion is to use the RPS Battery system for no longer than 6hours with pro coils and maybe 7 with standard coils. Other than that, they could have lost another 200grams in weight if they had used a strong plastic box, but hey 800grams is better than 2Kilos!! B) Good one Bernd!

:woohoo::woohoo::woohoo:
Regards Ismael

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